title: Conversion of proteins into biofuels by engineering nitrogen flux.
abstract: Biofuels are currently produced from carbohydrates and lipids in feedstock. Proteins, in contrast, have not been used to synthesize fuels because of the difficulties of deaminating protein hydrolysates. Here we apply metabolic engineering to generate Escherichia coli that can deaminate protein hydrolysates, enabling the cells to convert proteins to C4 and C5 alcohols at 56% of the theoretical yield. We accomplish this by introducing three exogenous transamination and deamination cycles, which provide an irreversible metabolic force that drives deamination reactions to completion. We show that Saccharomyces cerevisiae, E. coli, Bacillus subtilis and microalgae can be used as protein sources, producing up to 4,035 mg/l of alcohols from biomass containing ∼22 g/l of amino acids. These results show the feasibility of using proteins for biorefineries, for which high-protein microalgae could be used as a feedstock with a possibility of maximizing algal growth and total CO(2) fixation.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, California, USA.
authors.forename: Yi-Xin
authors.initials: YX
authors.lastname: Huo
authors.forename: Kwang Myung
authors.initials: KM
authors.lastname: Cho
authors.forename: Jimmy G Lafontaine
authors.initials: JG
authors.lastname: Rivera
authors.forename: Emma
authors.initials: E
authors.lastname: Monte
authors.forename: Claire R
authors.initials: CR
authors.lastname: Shen
authors.forename: Yajun
authors.initials: Y
authors.lastname: Yan
authors.forename: James C
authors.initials: JC
authors.lastname: Liao
mesh_terms: D000438:Alcohols / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism; D001412:Bacillus subtilis / Q000254:growth & development / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D056804:Biofuels; D018533:Biomass; D000440:Butanols / Q000378:metabolism; D003641:Deamination; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism; D005820:Genetic Testing; D058086:Microalgae / Q000378:metabolism; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism*; D010957:Plasmids; D015202:Protein Engineering / Q000379:methods*; D011506:Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000254:growth & development / Q000378:metabolism
chemical_list: D000438:Alcohols; D000596:Amino Acids; D001426:Bacterial Proteins; D056804:Biofuels; D000440:Butanols; D011506:Proteins; C040507:isobutyl alcohol; D009584:Nitrogen